Improve CLI error messages and recovery guidance

[Nanle-code]

Summary:
Several error paths in the CLI are too generic or incomplete. Contributors and users would benefit from more actionable messaging.

Why this matters:
Clear error messages reduce frustration and help users resolve issues quickly without relying on the maintainer team.

Proposed work:

• Standardize error formatting across commands
• Add practical next steps for common failures
• Improve validation messages before actions are executed

Acceptance criteria:

• Errors include clear context and suggested actions
• Users can identify what went wrong without guesswork
• Common failure cases are documented in output

[Jonathan-ai9]

@Jonathan-ai9 has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

Hi,I’d like to work on this issue. I will improve CLI error handling by standardizing error messages, adding actionable recovery guidance, and enhancing validation feedback so users can quickly understand and resolve common issues.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Jonathan-ai9 to this issue.